If you secretly think you've worked out the answer, then carefully click on the title.

I kept a secret no one knew,

I laid some plans that never grew,

For you and for each mouse to climb

at even my auspicious time,

So don't give up until you've got

There give to it my shot.

'I love a good secret. I try to tell everyone.'
'I know, you told me three times about my surprise birthday plan.'
'And weren't you excited to hear the secret?'

Riddle Answer The Best

Riddle Explanation
I kept a secret no one knew - the best-kept secret.

I laid some plans that never grew, for you and for each mouse to climb - the best laid plans of mice and men oft go astray.

at even my auspicious time - at the best of times.

so don't give up until you've got there give to it my shot - to give it one's best shot.